During drilling operations for the extraction of hydrocarbons, a variety of monitoring techniques are used to provide or record real-time data from the vicinity of a drill bit. Measurements of the surrounding subterranean formations may be made throughout drilling operations using downhole measurement and logging tools, such as measurement-while-drilling (MWD) and/or logging-while-drilling (LWD) tools, which help characterize the formations and aid in making operational decisions. Wellbore logging tools make measurements that may be used to determine the electrical resistivity (or its inverse, conductivity) of the formations being penetrated, where the electrical resistivity indicates various features of the formations. Those measurements may be taken using one or more antennas coupled to or otherwise associated with the wellbore logging tools.
Some logging tool antennas are formed by positioning a non-magnetic, non-conductive bobbin about an axial section of the logging tool, such as a drill collar, and subsequently wrapping a coil winding about the outer circumference of the bobbin. A protective layer is then often formed about the bobbin to secure the bobbin and the coil winding to the drill collar and protect the internal components of the antenna from potentially harmful downhole environments.